FIG. 1 (Prior Art) is a diagram of one traditional LED driver circuit. An Active Power Factor Correction (APFC) LED driver 10 provides a constant current output for the LED load. The output current of the APFC LED driver 10 contains a ripple current, while its average current is regulated and kept constant.
The ripple current is usually twice the input AC line frequency, for example, if the line frequency is 60 Hz, the constant current output of APFC LED driver 10 contains a 120 Hz current ripple.
A filtering capacitor C1 filters the output current of the APFC LED driver 10 and reduces the ripple current in the LED load. However, since the ripple current frequency is low (120 Hz), even with a large size capacitor, the LED load current still contains a ripple current of 120 Hz frequency.
Since the LED load current contains a line frequency ripple, the luminance output of the LED lamp also contains a line frequency flicker. The line frequency flicker may interfere with video equipment such as cameras and video recorders.